Circadian Rhythms

The release of blood stem cells into the bloodstream is regulated by circadian rhythms, according to research in in Nature. The work suggests that release of haematopoietic stem cells (HSCs) during an animal's resting period could promote the regeneration of blood stem cell populations and potentially other tissues.

HSCs circulate through the bloodstream and can home into sites throughout the body. Paul Frenette and colleagues show that this traffic is not random but follows a rhythmic pattern. Normal circadian oscillations can be disrupted by changes in the light rhythms, for example after exposure to constant light or a jet lag. Expression of the chemokine CXCL12 in the stem cell niche corresponds to the circadian oscillations; this is a result of adrenergic signals locally delivered by nerves in the bone marrow.

The research demonstrates that the central nervous system can directly regulate the function of a stem cell niche in peripheral tissues. The team also believes that this knowledge could help to increase the yield of HSCs if stem cells are harvested at the right time.